Control circuit



y 29, 1941- A. HOROWITZ ETAL 2,251,054

CONTROL CIRCUIT Filed Dec. 16, 1.938

Fig.

INVENTORS ALEXANDRE HOROWITZd JA. 0 l/IMMMEW A'i'ToRNEY Patented July 29, 1941 UNITED STATES PATENT OFFICE CONTROL CIRCUIT Application December 16, 1938, Serial No. 246,088 In Germany December 28, 1937 4 Claims.

This invention relates to a wireless receiving set capable of being tuned automatically to a number of predetermined stations by means of a station-selector constituted by a key-board, a selection disc or the like.

Wireless receivers having automatic tuning and incorporating a reversible motor for driving the tuning means have been developed in which the shaft of the tuning condensers carries a number of profiled discs each of which corresponds to one of the stations to which the receiver can be tuned automatically. An arrangement of this type is shown and described in Garrett United States Patent No. 1,956,419.

It has been found that when extremely accurate setting of the tuning means is required precautions must be taken to assure that the tuning motor is stopped at exactly the same position irrespective of whether the desired position oi? the tuning means is approached from one or the other direction.

The present invention has for one of its objects to provide, with a view of obtaining automatic tuning, an improved arrangement in which the position 01' the tuning means in which the motor is stopped is independent of the direction from which the desired position of the tuning means is reached.

In apparatus to which the present invention relates the driving direction of the tuning means and the stopping of the tuning means on the desired tuning position being reached is governed similarly to that described in the above mentioned patent, that is, by the position of one or more switches which are operated, for each of the predetermined stations, by the movement of a feeler which follows the periphery of a profiled body which is driven simultaneously with the tuning means.

According to the invention, a wireless receiving set of this kind is arranged in such manner that during its movement the feeler operates two switches which, in closed position, bring about the drive of the tuning means in one or the other direction respectively and that the switch for the drive in one direction is closed before the switch for the drive in the other direction is opened,

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully, by way of example, with reference to the accompanying drawing. Insaid drawing Figure 1 illustrates in schematic form a circuit arrangement incorporating the features of the present invention; and, Figure 2 illustrates a preferred embodiment of the invenion.

In the arrangement shown in Fig. 1, a feeler l is secured to a resilient contact tongue 13 which is associated with two further contact tongues I4 and I5, In the position of the disc 2 which is shown in the figure and in which the feeler engages the part 4 of the periphery of disc 2, the contact tongue I3 is lifted to such an extent that the contact point ll secured to this tongue engages the contact tongue It. The latter has thus been lifted from its neutral position in which neutral position the tongues l4 and I! are in electrical contact. When the switch 9 is closed, the coil ll of the motor that drives the shaft I is connected into the circuit, whereas, the coil 10 is cut off. The motor consequently operates the shaft I in a clockwise direction. If on the contrary the feeler 5 engages the part 3 of the periphery of the disc 2 the contact tongue l3 has descended to such extent that the point l'l no longer engages the contact tongue 14 with the result that the latter engages the contact tongue l5. When the switch 9 is closed in this case the coil 10 of the motor is connected into the circuit and the coil II is cut off, the motor thus driving the shaft i in an anti-clockwise direction.

If the receiving set is to be tuned to a given station the switch 9 that corresponds to this station is closed by means of the station selector. The motor then starts to move in a direction governed by the position or the disc 2 that corresponds to the desired station. If, as is shown in the figure, the feeler 5 engages, for example, the part 4 of the periphery of the disc 2 the shaft 1 is driven in a clockwise direction. This drive is continued until the feeler reaches the part II of the periphery of the disc 2, where the two parts of the periphery having different radii merge into each other. As soon as the feeler engages the part l2 of the periphery the contact tongue l3 starts to descend. In one position of the disc the contact tongue III has descended to such extent that the tongue l4 makes contact with the tongue l5. At this moment the two coils l0 and H of the motor are energized at the same time so that the field of the motor is entirely removed and the motor stops.

When the same station is selected in a position of the disc 2 in which the feeler engages the part 3 of the periphery the desired position of the tuning means is reached from an opposite direction. In this case the switch formed by the contact tongues It and I5 is closed at first and the shaft l is consequently driven in an anti-clockwise direction. This drive is continued until the feeler engages the part 12 of the periphery of the disc. As soon as the feeler reaches this part of the periphery the contact tongue I3 is lifted and in exactly the same position of the disc in which the tongues 14 and I5 engage each other in the case described above the contact between the tongues l3 and I4 is established. At this moment, the switches l3, l4 and l4, l5 are again closed at the same time so that the field of the motor is removed and the tuning means are caused to stop.

The motor is consequently cut off in exactly the same position of the disc 2 whatever the direction from which the desired position of the tuning means may be reached.

As is clear from the foregoing, on the desired tuning position being reached the two energizing coils l and I i of the motor are connected into the circuit at the same time so that the field of the motor is removed. As a matter of fact the counter-electromotive force supplied by the motor thus disappears at the same time. In order to prevent short circuit of the motor in this case the latter has connected in series with it a choke l6 which, on the desired tuning being reached, limits the current that passes through the coils ill and M to an admissible value. For this purpose, the choke 46 must be possessed of a rather substantial inductance and consequently is rather costly. Figure 2 shows a form of construction in which the choke can be dispensed with.

In the arrangement shown in Fig. 2, two alternating current relays A and B instead of the energizing coils i0 and H of the motor are connected into the circuit by the switches I3, 14 and M, E5. The relay A is connected into the circuit when the switches 8 and i3, N are closed, whereas the relay B is connected into the circuit when the switches 9 and l4, l are closed. Each of the relays A and 13 includes a rest contact in and b1 respectively and a working contact (12 and be respectively. The energizing coil ID of the motor is connected to the alternating current supply through the contacts a1 and b2, whereas the coil ii is connected to the supply through the contacts in and 0.2. On the relay A being energized the contact 111 is opened and the contact a2 is closed so that the coil H alone is con nected into the circuit. On the relay B being energized the coil I8 is connected into the circuit in a similar manner.

On the correct tuning being obtained the switches 3, M and M, 15 are closed at the same time and both relays A and B are thus energized and in this case the contacts (11 and in are opened and both energizing coils H! and H are thus cut off. Simultaneous energizing of the coils if) and ii is thus avoided in this arrangement so that the choke l6 can be dispensed with.

The operation of the arrangement shown 11 Fig. 2 otherwise corresponds to that of the arrangement shown in Fig. 1.

We claim:

1. In a control system, an operable shaft, a reversible motor for operating the shaft, said motor being provided with a pair of windings arranged so that energization of one thereof causes the motor to operate in one direction, whereas energization of the other winding causes the motor to operate in the opposite direction, a relay, acting upon operaton, to cause energization of one of said motor windings, a second relay acting upon operation to cause energization of the other of said motor windings, an operable main switch, a muiti-positionselectively operable switching means arranged so that with the main switch closed it causes the energization of one of said relays when in one position, the energization of the other of said relays when in another position and the energization of both of said relays when in an intermediate position, means connected to said shaft for controlling the positioning of said selectively operable switching means in accordance with the position of the shaft, and means effective only when both of said relays are in an energized condition at the same time for preventing energization of either of said motor windings whereby the motor is rendered inoperative.

2. In a shaft positioning system, a rotatable shaft, a reversible motor for driving said shaft, a source of energizing current for said motor, a pair of operable relay means, one of said relay means acting upon energization and only when the other of the relay means is de-energized, to connect the motor to said source and thereby effect the operation of the motor in one direction, said other relay means acting upon energization and only when the first relay means is de-energ ized, to connect the motor to said source and thereby effect the operation of the motor in the reverse direction, a multi-postion selectively operable switching means arranged so that it connects one of said relays across the source when in one position, the other of said relays across the source when in another position and both of said relays across the source when in an intermediate position, means connected to said shaft for controlling the positioning of said multiposition switching means in accordance with the position of the shaft, and means rendered operative when both of said relays are energized at the same time for connecting the motor from said source to thereby render the motor inoperative.

3. The arrangement disclosed in claim 2 in combination with a second pair of operable relay means one thereof acting upon energization and only when the other of said second pair is deenerg ized, to connect the motor to the source and thereby effect the operation of the motor in one direction, the other of said second pair of relay means acting upon energization and only when the first mentioned one of said second pair is de-energized to connect the motor to said source and thereby effect the operation of the motor in the reverse direction, a second multi-positioned selectively operable switching means arranged so that it connects one of said second pair of relays across the source when in one position, the other of said second pair of relays across the source when in another position and both of said second pair of relays across the source when in an intermediate position, means connected to said shaft for controlling the positioning of said second named multi-positioned switching means in accordance with the position of the shaft, and means rendered operative when both of said relays are energized at the same time for disconnecting the motor from said source.

4. In a shaft positioning means, an operable shaft, a reversible motor for operating said shaft, a source of current for said motor, a pair of circuits adapted to connect the motor to the source and arranged so that connection of the motor to the source through one of said circuits causes the motor to operate in one direction whereas connection of the motor to the source through the other of said circuits causes the motor to operate in the opposite direction. a plurality of sets of relays, each of said sets including a relay which acts upon operation to eflect the connection of the motor to the source through one oi said circuits and a relay which acts upon operation to effect the connection of the motor to the source through the other of said circuits, a plurality of main switches one for each oi said sets of relays, a plurality oi multi-position selectively operable switching means one for each gized when the switching means is in one position, the other relay of that set is energized when the switching means is in another position and both relays oi the set are energized when the switching means is in an intermediate posimeans in accordance with the position of said shaft, and operable means in said first named pair of circuits controlled by said relays for preventing the energizatlon of said motor when both relays of any of said sets of relays are in an or said sets of relays, each of said selectively 15 energized condition at the same time.

operable switching means being arranged so that upon closure of the main switch corresponding to any set one of the relays of the set is ener- .ALEXAN'DRE HOROWITZ. JOHANNES moms v. LAMMEREN GUNNAR. BORGE mos. 

